3 files changed, 127 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-class-devfreq b/Documentation/ABI/testing/sysfs-class-devfreq
index e672ccb02e7f..40f98a9428dc 100644
--- a/Documentation/ABI/testing/sysfs-class-devfreq
+++ b/Documentation/ABI/testing/sysfs-class-devfreq
@@ -44,6 +44,17 @@ Description:
                 (/sys/class/devfreq/.../central_polling is 0), this value
                 may be useless.
 
+What:           /sys/class/devfreq/.../trans_stat
+Date:           October 2012
+Contact:        MyungJoo Ham <myungjoo.ham@samsung.com>
+Descrtiption:
+                This ABI shows the statistics of devfreq behavior on a
+                specific device. It shows the time spent in each state and
+                the number of transitions between states.
+                In order to activate this ABI, the devfreq target device
+                driver should provide the list of available frequencies
+                with its profile.
+
 What:           /sys/class/devfreq/.../userspace/set_freq
 Date:           September 2011
 Contact:        MyungJoo Ham <myungjoo.ham@samsung.com>
diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index c44e562bdfe0..bf6de38190cf 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -66,6 +66,51 @@ static struct devfreq *find_device_devfreq(struct device *dev)
         return ERR_PTR(-ENODEV);
 }
 
+/**
+ * devfreq_get_freq_level() - Lookup freq_table for the frequency
+ * @devfreq:    the devfreq instance
+ * @freq:       the target frequency
+ */
+static int devfreq_get_freq_level(struct devfreq *devfreq, unsigned long freq)
+{
+        int lev;
+
+        for (lev = 0; lev < devfreq->profile->max_state; lev++)
+                if (freq == devfreq->profile->freq_table[lev])
+                        return lev;
+
+        return -EINVAL;
+}
+
+/**
+ * devfreq_update_status() - Update statistics of devfreq behavior
+ * @devfreq:    the devfreq instance
+ * @freq:       the update target frequency
+ */
+static int devfreq_update_status(struct devfreq *devfreq, unsigned long freq)
+{
+        int lev, prev_lev;
+        unsigned long cur_time;
+
+        lev = devfreq_get_freq_level(devfreq, freq);
+        if (lev < 0)
+                return lev;
+
+        cur_time = jiffies;
+        devfreq->time_in_state[lev] +=
+                         cur_time - devfreq->last_stat_updated;
+        if (freq != devfreq->previous_freq) {
+                prev_lev = devfreq_get_freq_level(devfreq,
+                                                devfreq->previous_freq);
+                devfreq->trans_table[(prev_lev *
+                                devfreq->profile->max_state) + lev]++;
+                devfreq->total_trans++;
+        }
+        devfreq->last_stat_updated = cur_time;
+
+        return 0;
+}
+
 /* Load monitoring helper functions for governors use */
 
 /**
@@ -112,6 +157,11 @@ int update_devfreq(struct devfreq *devfreq)
         if (err)
                 return err;
 
+        if (devfreq->profile->freq_table)
+                if (devfreq_update_status(devfreq, freq))
+                        dev_err(&devfreq->dev,
+                                "Couldn't update frequency transition information.\n");
+
         devfreq->previous_freq = freq;
         return err;
 }
@@ -378,6 +428,15 @@ struct devfreq *devfreq_add_device(struct device *dev,
         devfreq->data = data;
         devfreq->nb.notifier_call = devfreq_notifier_call;
 
+        devfreq->trans_table =  devm_kzalloc(dev, sizeof(unsigned int) *
+                                                devfreq->profile->max_state *
+                                                devfreq->profile->max_state,
+                                                GFP_KERNEL);
+        devfreq->time_in_state = devm_kzalloc(dev, sizeof(unsigned int) *
+                                                devfreq->profile->max_state,
+                                                GFP_KERNEL);
+        devfreq->last_stat_updated = jiffies;
+
         dev_set_name(&devfreq->dev, dev_name(dev));
         err = device_register(&devfreq->dev);
         if (err) {
@@ -601,6 +660,47 @@ static ssize_t show_available_freqs(struct device *d,
         return count;
 }
 
+static ssize_t show_trans_table(struct device *dev, struct device_attribute *attr,
+                                char *buf)
+{
+        struct devfreq *devfreq = to_devfreq(dev);
+        ssize_t len;
+        int i, j, err;
+        unsigned int max_state = devfreq->profile->max_state;
+
+        err = devfreq_update_status(devfreq, devfreq->previous_freq);
+        if (err)
+                return 0;
+
+        len = sprintf(buf, "   From  :   To\n");
+        len += sprintf(buf + len, "         :");
+        for (i = 0; i < max_state; i++)
+                len += sprintf(buf + len, "%8u",
+                                devfreq->profile->freq_table[i]);
+
+        len += sprintf(buf + len, "   time(ms)\n");
+
+        for (i = 0; i < max_state; i++) {
+                if (devfreq->profile->freq_table[i]
+                                        == devfreq->previous_freq) {
+                        len += sprintf(buf + len, "*");
+                } else {
+                        len += sprintf(buf + len, " ");
+                }
+                len += sprintf(buf + len, "%8u:",
+                                devfreq->profile->freq_table[i]);
+                for (j = 0; j < max_state; j++)
+                        len += sprintf(buf + len, "%8u",
+                                devfreq->trans_table[(i * max_state) + j]);
+                len += sprintf(buf + len, "%10u\n",
+                        jiffies_to_msecs(devfreq->time_in_state[i]));
+        }
+
+        len += sprintf(buf + len, "Total transition : %u\n",
+                                        devfreq->total_trans);
+        return len;
+}
+
 static struct device_attribute devfreq_attrs[] = {
         __ATTR(governor, S_IRUGO, show_governor, NULL),
         __ATTR(cur_freq, S_IRUGO, show_freq, NULL),
@@ -610,6 +710,7 @@ static struct device_attribute devfreq_attrs[] = {
                store_polling_interval),
         __ATTR(min_freq, S_IRUGO | S_IWUSR, show_min_freq, store_min_freq),
         __ATTR(max_freq, S_IRUGO | S_IWUSR, show_max_freq, store_max_freq),
+        __ATTR(trans_stat, S_IRUGO, show_trans_table, NULL),
         { },
 };
 
diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
index 1461fb2355ad..bc35c4aee6a3 100644
--- a/include/linux/devfreq.h
+++ b/include/linux/devfreq.h
@@ -73,6 +73,8 @@ struct devfreq_dev_status {
  *                      from devfreq_remove_device() call. If the user
  *                      has registered devfreq->nb at a notifier-head,
  *                      this is the time to unregister it.
+ * @freq_table: Optional list of frequencies to support statistics.
+ * @max_state:  The size of freq_table.
  */
 struct devfreq_dev_profile {
         unsigned long initial_freq;
@@ -83,6 +85,9 @@ struct devfreq_dev_profile {
                               struct devfreq_dev_status *stat);
         int (*get_cur_freq)(struct device *dev, unsigned long *freq);
         void (*exit)(struct device *dev);
+
+        unsigned int *freq_table;
+        unsigned int max_state;
 };
 
 /**
@@ -127,6 +132,10 @@ struct devfreq_governor {
  * @min_freq:   Limit minimum frequency requested by user (0: none)
  * @max_freq:   Limit maximum frequency requested by user (0: none)
  * @stop_polling:        devfreq polling status of a device.
+ * @total_trans:        Number of devfreq transitions
+ * @trans_table:        Statistics of devfreq transitions
+ * @time_in_state:      Statistics of devfreq states
+ * @last_stat_updated:  The last time stat updated
  *
  * This structure stores the devfreq information for a give device.
  *
@@ -153,6 +162,12 @@ struct devfreq {
         unsigned long min_freq;
         unsigned long max_freq;
         bool stop_polling;
+
+        /* information for device freqeuncy transition */
+        unsigned int total_trans;
+        unsigned int *trans_table;
+        unsigned long *time_in_state;
+        unsigned long last_stat_updated;
 };
 
 #if defined(CONFIG_PM_DEVFREQ)